Non-toxic reinforcement of structures in high moisture environments

ABSTRACT

Reinforcement of structures in high moisture environments is achieved by applying reinforcement layers which include a fabric portion ( 34 ) and an uncured resin portion ( 56 ) where the uncured resin contains a conversion agent and a thickening agent. The uncured reinforcement layer ( 44 ) is cured in place about the structure to form a composite reinforcement shell ( 32 ). The uncured reinforcement layer ( 44 ) is formed from woven or stitched unidirectional fabric. The invention finds particular use in reinforcing bridge supports and pilings which are at least partially submerged in water. Containment layers are used to prevent resin dilution and de-lamination during curing of the reinforcement structure. The resin used is non-toxic with respect to aquatic wildlife.

This Application is 371 of PCT/US99/27860 filed Nov. 23, 1999 which is acont of Ser. No. 09/198,642 filed Nov. 24,1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to reinforcing large scalesupport structures which are present in high moisture environments. Moreparticularly, the present invention involves reinforcing structureswhich are at least partially immersed in either fresh or salt water.Reinforcement is accomplished utilizing composite materials which arewrapped around the structures in situ to form underwater reinforcements.The invention is intended for use in those environments where toxicityto fish and other aquatic wildlife may be of concern.

2. Description of Related Art

Concrete columns are widely used as support structures. Bridge supports,freeway overpass supports, building structural supports and parkingstructure supports are just a few of the many uses for concrete columns.Concrete columns exist in a wide variety of shapes. Concrete columnswith circular, square and rectangular cross-sections are most common.However, numerous other cross-sectional shapes have been used includingregular polygonal shapes and irregular cross-sections. The size ofconcrete columns also varies greatly depending upon the intended use.Concrete columns with diameters on the order of 2 to 20 feet and lengthsof well over 50 feet are commonly used as bridge or overpass supports.

It is common practice to reinforce concrete columns with metal rods orbars. The metal reinforcement provides a great deal of added structuralstrength to the concrete column. Although metal reinforcement ofconcrete columns provides adequate structural reinforcement under mostcircumstances, there have been numerous incidents of structural failureof metal-reinforced concrete columns when subjected to asymmetric loadsgenerated during earthquakes. The structural failure of a metalreinforced concrete support column during an earthquake can havedisastrous consequences. Accordingly, there is a continuing need toenhance the ability of concrete columns to withstand the asymmetricloads which are applied to the column during an earthquake.

One way of increasing the structural integrity of concrete columns is toinclude additional metal reinforcement prior to pouring the concretecolumn. Other design features may be incorporated into the concretecolumn fabrication in order to increase its resistance to asymmetricloading. However, there are hundreds of thousands of existing concretesupports located in earthquake prone areas which do not have adequatemetal reinforcement or structural design to withstand high degrees ofasymmetric loading. Accordingly, there has been a concentrated effort todevelop systems for reinforcing such existing concrete columns toprevent or reduce the likelihood of failure during an earthquake.

One example of a method for increasing the structural strength ofexisting concrete structures is set forth in U.S. Pat. No. 4,786,341. Inthis particular patent, the outer surface of the concrete column isreinforced by wrapping a fiber around the column in a variety ofdifferent patterns. A problem with this particular method is the amountof time required to wrap a concrete column with a single fiber is timeconsuming and expensive.

One approach to reinforcing the exterior of an existing concrete supportcolumn is set forth in U.S. Pat. No. 5,043,033. In this patent, theexterior of the concrete column is wrapped with a composite material toform a shell surrounding the concrete column. The space between theouter composite shell and the concrete column is then pressurized byinjecting a hardenable liquid.

Another approach, as set forth in U.S. Pat. No. 5,218,810 involveswrapping large columns with composite reinforcement layers to form areinforcing shell which is in direct contact with the column surface.

Although the above reinforcement procedures are well-suited forreinforcing structures in relatively dry environments, they are notsuitable for use where water is present. For example, numerous bridgesupports columns include substantial portions which are located underwater. Such underwater columns are present in both fresh water and saltwater environments. Accordingly, there is a present need to providecomposite type reinforcement methods and systems which can be used underwater. One such method is described in PCT International Publication No.WO 97/44188.

In addition to concrete columns, there are numerous other types ofstructures present in high moisture environments which require periodicreinforcing. Pier or pilings in both fresh water and salt water are madefrom many different types of materials, including metal, wood andconcrete. These types of structures are subject to continualdeterioration from the elements. A method and system which can be usedsimply and efficiently to rehabilitate these types of structures wouldbe extremely advantageous. It also would be desirable to provide suchreinforcing structures without creating a toxic hazard to fish and otherwildlife.

SUMMARY OF THE PRESENT INVENTION

In accordance with the present invention, a method is provided forreinforcing a wide variety of structures which are located underwater orin other high moisture environments. The invention is based on thediscovery that composite materials may be used successfully to reinforcestructures in high moisture environments provided that certain epoxyresin compositions are utilized in the resin matrix of the composite.

The invention involves applying to the surface of the structure at leastone uncured reinforcement layer to form an uncured shell surrounding thesurface. The uncured reinforcement layer includes a fabric portion andan uncured resin portion. As a feature of the present invention, theuncured resin portions contains 80-120 parts by weight epoxy resin and30-70 parts by weight of a conversion agent. Optionally, 1-10 parts byweight of a thickening agent may be included in the uncured resin. Thistype of resin, when cured, was found to be especially well-suited foruse in providing high strength reinforcement structures in high moistureenvironments. The uncured resin may also contain up to 10 parts byweight or more of a coloring agent. The coloring agent is useful when itis desirable to hide underlying surface irregularities, such as cracks,or to otherwise provide a desired surface color.

As another feature of the present invention, a containment layer isplaced around the uncured reinforcement layer to enhance the curingprocess in underwater situations or other high moisture environments.The use of stretch wrap as a containment layer is especially useful forsupport columns and other structures located in river or oceanenvironments where turbulent water flow or wave action presents uniqueproblems with respect to applying and curing the compositereinforcement.

As an additional feature of the present invention, it was discoveredthat the above-specified resins were not toxic to aquatic life duringthe application and curing in underwater conditions.

The above discussed and many other features and attendant advantages ofthe present invention will become better understood by reference to thefollowing detailed description when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a platform which includes partially submergedsupport structures which include four exemplary reinforcements inaccordance with the present invention.

FIG. 2 is a sectional view of one of the reinforcements of FIG. 1 takenin the 2—2 plane.

FIG. 3 is a partial schematic view of an exemplary uncured reinforcementlayer prior to application to the surface of a support structure.

DETAILED DESCRIPTION OF THE INVENTION

The present invention has wide application to the reinforcement of largestructures which are located either under water or in a high moistureenvironment. A high moisture environment is one where the structure isconsistently exposed to water or air which is saturated with water.Exemplary structures which may be reinforced include bridge supportcolumns, pilings and pier or platform support structures which are atleast partially submerged in either fresh or salt water. These types ofstructures are typically made from reinforced concrete, wood, metal andcombinations thereof.

An exemplary platform which is reinforced in a number of differentplaces is shown generally at 10 in FIG. 1.

The platform 10 includes a deck 12 and supporting columns 14 and 16.Both columns 14 and 16 are anchored to an ocean or lake floor 20 andextend above the lake or ocean surface 22. A cross support beam 24extends between the support columns 14 and 16. For exemplary purposes,the platform 10 is shown having four different exemplary types ofreinforcements at locations 26, 28, 30 and 32.

It will be understood by those skilled in the art that the platform 10is shown for exemplary purposes only, and that the reinforcement methodsand materials described herein with respect to this example may also beused to reinforce large-scale structures in other high-moistureenvironments.

A cross section of reinforcement structure or shell 32 is shown in FIG.2. The reinforcement shell includes a reinforcement layer comprising afabric portion 34 and a resin portion depicted as resin matrix 36. Theshell 32 surrounds the surface 40 of column 16. Column 16 in thisexample is concrete reinforced with steel. However, the column couldequally as well be made from wood or metal. The surface 40 of column 16defines a continuous surface around which the shell 32 has been formed.The reinforcement shell 32 further includes an exterior layer of stretchwrap which is shown in phantom at 42.

Referring to FIG. 3, a partial sectional schematic view of the shell isshown when it is in the form of an uncured reinforcement layer prior toapplication to the column surface 40. This uncured reinforcement layer44 includes the fabric portion 34 and the uncured resin portion 56. Uponcuring, the resin portion 56 becomes the cured resin matrix 36 shown inFIG. 2. The uncured reinforcement layer 44 has two selveges 50 and 52 asshown in FIG. 3. The width of the fabric “W” may be from 3 to 100 inchesor more. For shell 32, the width of the fabric is on the order of 4 to 6feet. Larger sizes become unmanageable at the job site, especially whendivers or other personnel must transport the uncured reinforcement layerunder water to the structure being reinforced.

The fabric portion 34 preferably includes a woven fabric which isimpregnated with resin prior to application to the structures. The wovenfabric may be made from any of the known fiber material commonly used inhigh strength composite structures. Exemplary fibers include glass,polyaramid, graphite, silica, quartz, carbon, ceramic and polyethylene.Preferably, the preferred fabric is a plain weave, predominantly warpunidirectional fabric comprised of a warp (0 degree orientation ofE-glass or carbon roving) and a weft (90 degree orientation) of E-glassand a thermoplastic adhesive. The ratio of warp to weft fiber is about17.5 to 1 by weight for glass and about 14 to 1 for graphite. In anotherorientation the fabric will extend at a plus bias angle of between about+20 to +70° relative to the selve edges and a minus bias angle ofbetween about −20 to −70° relative to the selve edges. The diameter ofthe fibers used in the woven fiber mat preferably range from about 3microns to about 30 microns depending on the particular fiber. It ispreferred that the fibers be bundled into yarns which include betweenabout 200 to 8,000 fibers. The fabric may also be a plain woven fabric,but may also be a 2 to 8 harness satin weave. The number of warp yarnsper inch is preferably between 40 to 60. The preferred number of fillyarns per inch is preferably between about 40 to 60. The particularweave pattern and orientation of fibers may be varied depending upon theparticular structure being reinforced. A woven mat may be stitched oradhesively bonded to the fabric.

The invention is particularly well-suited for reinforcing large columnsor pilings which have diameters on the order of 1 to 15 feet and whichhave lengths on the order of 10 to 50 feet or higher. The invention mayalso be used to reinforce beam connections in the same manner as setforth in PCT Application WO 97/01686.

The resin used to impregnate the fabric is an epoxy resin formulationwhich includes the epoxy resin, a conversion agent, an optionalthickening agent and an optional coloring agent. The ingredients arepreferably present in the amounts set forth in Table 1.

TABLE 1 Resin Ingredient Parts By Weight Epoxy Resin 80-120 ConversionAgent 30-70  Thickening Agent 0-10 Coloring Agent 0-10

Resin is preferably a two-part epoxy resin which is mixed at the siteand impregnated into a roll of woven or stitched fabric. Impregnatedfabric is then taken physically underwater by divers and wrapped aroundthe deteriorated structure. Part A of the epoxy resin preferablyincludes a hydrogenated bis A epoxy resin, the coloring agent or agents,if any, and the thickening agent. Part B contains the conversion agent.It is preferred that the bis A epoxy be hydrogenated since hydrogenatedepoxies are more resistant to ultraviolet light. Although any number ofdifferent hydrogenated bis A epoxy resins may be used, it is preferredthat EPALLOY 5,000, which is made by CVC Specialty Chemicals (MapleShade, N.J.) be utilized. An alternate preferred epoxy is available fromShell Oil Company (Houston, Tex.) under the tradename EPONEX 1510. Othersuitable resins include EPON 828 available from Shell Oil Company(Houston, Tex.); ARALDITE 6010 available from CIBA-GEIGY (Brewster,N.Y.); and DER 331 available from Dow Chemical (Midland, Mich.). Variousmixtures and blend of the resins may be used.

Silica particles are a preferred thickening agent with glass beads(Q-cells) or other known thickening agents being suitable. A preferredthickening agent is hydrophobic fumed silica which is available fromCabot (Tuscola, Ill.) under the tradename CAB-O-SIL TS720. It ispreferred that sufficient fumed silica or other thickening agent beadded in an amount that provides an uncured resin having a viscosity onthe order of 3,000 to 50,000 cps. The resin preferably is sufficientlyviscous so that it will not be leaked or otherwise flow from the fabricwhen it is taken underwater for application to the deterioratedstructured. On the other hand, the viscosity must be sufficiently low sothat the resin can be easily impregnated into the fabric usingconventional impregnation techniques.

Any of the known coloring agents may be utilized to provide desiredcolors to the epoxy resin. Preferred coloring agents include titaniumoxide and carbon black. The amount of titanium dioxide and/or carbonblack can be varied to achieve different coloring densities which mayvary, through varying shades of gray, from white to black. Titaniumdioxide available from DuPont (Wilmington, Del.) is available under thetradename TiPute R960. Carbon black may also be introduced into theresin in the form of JEFFCO BLACK which is a product available fromJeffco Products (San Diego, Calif.). JEFFCO BLACK is a 50/50 mixture byweight of bis A epoxy resin and carbon black.

The conversion agent is a polyaminoamid adduct that is only partiallywater soluble. The conversion agent is a proprietary product availablefrom WITCO (Bergkamen Germany) under the tradename EUREDUR 450. Othersuitable conversion agents include ANCHAMINE 2143 which is modifiedcycloaliphatic amine which is made by Air Products (Allentown, Pa.), andANCHAMINE 2280 which is a modified amine which is also made by AirProducts (Allentown, Pa.). Conversion agents which were found to not besuitable for use in accordance with the present invention includeVERSAMID 140 available from Henkel (LaGrange, Ill.) and GENAMID 151which is also available from Henkel. Both VERSAMID 140 and GENAMID 151become milky in water and therefore are potentially toxic to fish.Versamid 140 is too high in viscosity to dip for a viable resincandidate.

Other conversion agents which were tested and found not to be suitableinclude ANCHAMIDE 350A which is an imidazoline/amide made by AirProducts (Allentown, Pa.). The modulus of the resulting material is toolow. An alkylated phenolic polyamine conversion agent available fromCiba Polymers (Brewster, N.Y.) under the tradename HY3440 was also foundto have a relatively short cure time which is not well suited for use inthe present invention where cure times need to be fairly long in orderto allow impregnation of the resin into the fabric at the site followedby transport by divers to the submerged structure. The viscosity(1,000-3,000 cps) also had too large a range for practicality.

Other conversion agents which have one or more unsuitable propertiesinclude Gaskamine 328 which is a primary amine end capped poly metaxylylamine available from Mitsubishi Gas Chemical Company (Kanagawa,Japan). Gaskamine 328 gives a product which cures to a sticky state inwater and is therefore unsuitable. Anchamine 2353 (a modified polyamidefrom Air Products) had too low a modulus when cured. Suitable conversionagents should produce a resin having relatively long cure times (atleast about 4 hours) which can be exposed to water when the resin issubmerged as well as producing suitably strong resin matrix. EUREDUR450, ANCHAMINE 2143 and ANCHAMINE 2280 were found to have such desirableproperties. Conversion agents which have properties which are similar toEUREDUR 450, ANCHAMINE 2143 and ANCHAMINE 2280 may also be used.

Exemplary resin matrices in accordance with the present invention willinclude from 90-100 parts by weight EPALLOY 5,000 which is combined toform part A of the epoxy resin with 5 parts by weight CAB-O-SIL TS720and from 5 to 7 parts by weight titanium dioxide and 1 to 2 parts byweight JEFFCO BLACK. Part B is EUREDUR 450 which is added to Part A inan amount of from 45 to 55 parts by weight. A particularly preferred2-part resin will include 100 parts by weight EPALLOY 5,000, 6 parts byweight titanium dioxide, 5 parts by weight CAB-O-SIL TS720, and 1.25parts per weight JEFFCO BLACK. Part B is EUREDUR 450 which is added topart A in an amount of 48.9 parts by weight.

Another preferred exemplary 2-part epoxy which may be used as a suitableresin matrix contains 100 parts by weight Erysis GE 60 (epoxidizedsorbitol resin made by CVC chemical Specialties), 6 parts by weighttitanium dioxide, 2 parts by weight CAB-O-SIL TS720 with part B beingEUREDUR 450 which is added in an amount of about 80 parts by weight.Here the working time is short (about 30 minutes) and metered mixing atthe saturator rolls would be required for field suitability.

Once the uncured reinforcement layer has been wrapped around the column16, stretch wrap or other similar thin wrapping layer is wrapped overthe uncured shell to hold it in place. The stretch wrapping is shown inFIG. 2 as phantom layer 42. The stretch wrap is shown in phantom sinceit may be removed after final curing or, alternatively, it may be leftin place. Any of the commonly used stretch wrap materials may be used toprovide the containment layer 42. Stretch wrap is a polymer film whichis widely used and readily available from Mobil Oil Corporation underthe tradenames MOBILWRAP or MOBIL MASTERWRAP. The wrap is also sold byBorden Chemical Co. under the tradename BORDEN HANDWRAP, and is alsoavailable from Uline (Los Angeles, Calif.) under the tradename ULINEECONO-WRAPPER. Gauges 80-120.

Use of the stretch wrap is particularly preferred in situations wherethe column 16 is subjected to turbulence. For example, the use of astretch wrap containment layer 42 is particularly preferred wherereinforcing columns are located in areas where wave action or otherstrong ocean currents are present. Additionally, the use of stretch wrapis preferred in rivers where fast flowing and/or turbulent water may bepresent. Referring again to FIG. 1, three additional exemplaryreinforcements utilizing the composite shells in accordance with thepresent invention are shown at 26, 28 and 30. Reinforcement 28 isexemplary of the type of reinforcements where the uncured reinforcementlayer is wound spirally around column 14. In this type of spiralreinforcement system, the width of the uncured reinforcement layer willrange from a few inches to 2 to 3 feet. This type of spiral wrapreinforcement configuration is well-suited for situations where the useof wider fiber matting is not possible. Such situations may occur whereonly one diver is available or underwater conditions make it difficultto apply relatively wide reinforcement layers to the column or othersupport structure. When spiral wrapping, as depicted at 28, is used, itis particularly preferred that a final outer layer of stretch wrap beapplied to contain the spirally-wrapped reinforcement.

The reinforcement 26 shown in FIG. 1 is similar to the reinforcementshell 32 except that provision is made for extending the reinforcingshell onto horizontal structural beam 24. In addition, the reinforcementshell 26 extends above the water surface 22 and is further adhered tothe bottom of deck 12 as shown at 60 and 62.

A fourth exemplary composite reinforcement is shown at 30. This is alsoan example of using uncured reinforcement layers in accordance with thepresent invention to form a spirally-wrapped reinforcement. Thereinforcement 30 is based upon the same spiral wrapping principle asreinforcement 28, except that it has been adapted to providereinforcement of the attachment between vertical column 16 andhorizontal beam 24. The spiral wrapping shown in reinforcement 30 ispartially schematic and exemplary only. Those of ordinary skill in theart will recognize that any number of spiral wrapping orientations arepossible in order to achieve reinforcement of the joint between beam 24and column 16. For example, a typical wrapping of a column will notinvolve spiral wrapping. Instead, the fabric will be wrapped around thecolumn in a direction perpendicular to the column axis. The next fabriclayer is butt spliced against the first wrapping layer. Additionalvertically butt-jointed layers are added, as necessary, to cover theentire column (e.g. see U.S. Pat. No. 5,218,810). In addition, theon-site resin may be applied to the structure prior to reinforcement toact as a primer. Also, the on-site resin may be applied as a cosmeticcoating over the exterior of the reinforcement once it has been appliedto the structure. It is preferred that the resin have a working time offrom 3-5 hours in order to allow sufficient time for impregnation andapplication. However, working times as short as 45 minutes are suitable.

Examples of practice are as follows:

EXAMPLE 1

An underwater fabric is wrapped using glass fabric impregnated with aresin which is prepared at the job site. Glass fabric is provided at thejob site as a roll of material which has a width of 24 to 54 inches.Part A of the resin is made using EPALLOY 5,000, titanium dioxide,CAB-O-SIL TS720 and JEFFCO BLACK. The JEFFCO BLACK and titanium oxideare added first to the EPALLOY 5,000 and mixed until uniform. TheCAB-O-SIL is added last and stirred at least five minutes with a shearblade until the CAB-O-SIL is dispersed throughout the resin. Part A maybe mixed prior to arrival at the job site. At the job site, part B whichis EUREDUR 450 is stirred into the part A with the resulting mixture putinto the trough of a conventional saturator for use in saturating fabricas it is unwound from the roll. The amounts of various ingredients areadded to the mixtures to provide a resin which has 100 parts by weightEPALLOY 5,000, 6 parts by weight titanium dioxide, 5 parts by weightCAB-O-SIL TS720, 1.25 parts by weight JEFFCO BLACK, and 48.9 parts byweight EUREDUR 450.

As soon as the fabric is dipped through the saturator trough, a diverthen takes the fabric underwater where it is wrapped around thestructure. Immediately thereafter, the diver then wraps over theimpregnated cloth with polyethylene stretch wrap such as Uline stretchwrap sold by Uline Corporation (Waukegan, Ill.). In place of fiberglassfabric, stitched unidirectional graphite fabric of aerial weight 650grams per square meter may be used.

The above systems have viscosities which remain relatively constant forabout 4 hours which was found to be adequate time to allow mixing,impregnation and underwater wrapping. In addition, toxicity tests wereconducted. The tests showed that the resin system used in the presentinvention was not toxic to fish. The pH of the resin system is about 7.0so that toxicity based on pH is also not a problem.

EXAMPLE 2

The same basic procedure as outlined above was followed except that theresin used to impregnate either glass or graphite fabric has the formula

Part A: Erysis GE 60, 100 parts by weight; titanium dioxide 6 parts byweight; and CAB-O-SIL TS720, 2 parts by weight

Part B: EUREDUR 450, 67.6 parts by weight.

EXAMPLE 3A

The same basic procedure as in Example 1 above was followed, except thatthe resin used to impregnate either glass or graphite fabric had theformula:

Part A: Epon 828, 100 parts by weight; and titanium dioxide, 4 parts byweight;

Part B: EUREDUR 450, 61 parts by weight Epon 828 is a bis A epoxy fromShell Chemical (Houston, Tex.)

This resin has a working time of about 51 minutes so metered mixingprobably would be required at the saturator. Epon 828 gives a highermodulus product after cure than Epalloy 5,000. Various blends of Epalloy5,000 with Epon 828 can be used in the part A to adjust the working timeand hence the underwater cure time.

EXAMPLE 3B

The same basic procedure as in Example 1 above was followed, except thatthe resin used to impregnate either glass or graphite fabric had theformula:

Part A: Epon 828, 100 parts by weight; titanium dioxide, 4 parts byweight

Part B: ANCHAMINE 2143, 61.5 parts by weight

The resin has a working time of about 58 minutes so metered mixingprobably would be required at the saturator.

EXAMPLE 3C

The same basic procedure as in Example 1 above was followed, except thatthe resin used to impregnate either the glass or graphite fabric had theformula:

Part A: Epon 828, 100 parts by weight; titanium dioxide, 4 parts byweight

Part B: ANCHAMINE 2280; 58.8 parts by weight

This resin has a working time of about 55 minutes so metered mixingprobably would be required at the saturator.

Two ply 60% by weight resin content panels were made from the resins inExamples 3A, 3B and 3C on HEX 3R 103 graphite fabric. 103 fabric is 18oz/yd² or ounce per square yard aerial weight, mostly unidirectionalwith about 1.5% by weight thermoplastic thread that is heat set to holdthe graphite fibers together. The resin ingredients were mixed togetherby stirring about 5 minutes then approximately half was poured on to theprecut fabric, and then the resin was squeegied on with a stiff rubberplate. A second ply was added similarly with more resin squeegied on thetop. This would simulate running the fabric through the saturator.

Two types of panels were made—those cured in air and those curedunderwater (both fresh and saltwater). The air cured panels were made ona flat surface lined with smooth polyethylene with the top surfaces opento the air. The underwater cured panels were made by first impregnatingthe 103 fabric with resin as described above, but then lifting the wetprepreg and inserting it in either fresh or saltwater for enough time tothoroughly wet the prepreg, then putting this wet prepreg on a flatacrylic board. A second ply was made the same way and placed over thefirst. This water wet uncured two ply prepreg on the acrylic board wasthen wrapped with about three layers of stretch wrap and placed ineither fresh or salt water. After 8 days the panel was removed, quicklycut into sections, the 8 day cure pieces were tested and the remainingwere returned to the water for longer soakings (the stretch wrapremoved). Room temperature tensile testing was then done on the panelswith the following results as shown in Tables 2 and 3.

TABLE 2 FRESHWATER Example Cure Type Tensile Strength (ksi) Tensile Mod(msi) 3 dry cure* 115 10.3  8 days underwater 79 9.7 60 days underwater96 9.6 3A dry cure* 106 10.4  8 days underwater 116 10.2 60 daysunderwater 113 10.1 3B dry cure* 104 9.4  8 days underwater 115 9.8 60days underwater 109 10.1 All values are normalized to 80 mils forcomparison *at least 5 days at room temperature followed by a 48 hour140° F. post cure

TABLE 3 SALTWATER Example Cure Type Tensile Strength (ksi) Tensile Mod(msi) 3 dry cure* 115 10.3  8 days underwater 84 8.9 60 days underwater94 9.1 3A dry cure* 106 10.4  8 days underwater 88 8.9 60 daysunderwater 95 9.1 3B dry cure* 104 9.4  8 days underwater 105 9.9 60days underwater 103 9.6 All values are normalized to 80 mils forcomparison *at least 5 days at room temperature followed by a 48 hour140° F. post cure

COMPARATIVE EXAMPLE 4

The same basic procedure as in Example 1 above was followed, except thatthe resin used to impregnate either glass or graphite fabric had theformula:

Part A: ERL4221, 100 parts by weight; titanium dioxide, 6 parts byweight; and CAB-O-SIL TS720, 6 parts by weight

Part B: Euredur 450, 83.9 parts by weight

ERL4221 is a cycloaliphatic epoxy resin made by Union Carbide (Danbury,Conn.). This resin system does not cure at room temperature.

COMPARATIVE EXAMPLE 5

The same basic procedure as in Example 1 above was followed, except thatthe resin used to impregnate either glass or graphite fabric had theformula:

Part A: Erysis GE30, 100 parts by weight, titanium dioxide, 6 parts byweight, CAB-O-SIL TS720, 6 parts by weight

Part B: Euredur 450, 80.7 parts by weight GE30 is trimethanolpropanetriglydyl ether made by CVC Chemical Specialties. This system was stickyafter cure and therefore unsuitable.

Having thus described exemplary embodiments of the present invention, itshould be noted by those skilled in the art that the disclosures hereinare exemplary only and that various other alternations, adaptations andmodifications may be made within the scope of the present invention.Accordingly, the present invention is not limited to the specificembodiments as illustrated herein.

What is claimed is:
 1. A method for reinforcing structures in highmoisture environments wherein said structure comprises at least onesurface that is located underwater, said method comprising the steps of:applying to said surface at least one uncured reinforcement layer toform an uncured shell on said surface, said reinforcement layercomprising a fabric portion and an uncured resin portion, said uncuredresin portion comprising: 80-120 parts by weight epoxy resin and 30-70parts by weight of a conversion agent; and curing said uncured resin toform a composite shell for reinforcing said structure.
 2. A method forreinforcing structures in high moisture environments according to claim1 wherein said uncured resin portion comprises 1 to 10 parts by weightof a thickening agent.
 3. A method for reinforcing structures in highmoisture environments according to claim 1 which includes the additionalstep of placing a containment layer over said uncured shell prior tocuring thereof.
 4. A method for reinforcing structures in high moistureenvironments according to claim 1 wherein said uncured resin portionfurther comprising from 0.1 to 10 parts per weight of a coloring agent.5. A method for reinforcing structures in high moisture environmentsaccording to claim 1 wherein said fabric portion comprises a woven fibermat wherein said fiber is selected from the group consisting of glass,polyaramid, graphite, silica, quartz, carbon, ceramic and polyethylene.6. A method for reinforcing structures in high moisture environmentsaccording to claim 1 wherein said epoxy resin is a hydrogenated epoxyresin.
 7. A method for reinforcing structures in high moistureenvironments according to claim 4 wherein said coloring agent isselected from the group consisting of carbon black and titanium dioxide.8. A method for reinforcing structures in high moisture environmentsaccording to claim 1 wherein said conversion agent is a polyamino acidadduct, cycloaliphatic amine or modified amine.
 9. A method forreinforcing structures in high moisture environments according to claim3 wherein said containment layer comprises stretch wrap.
 10. A structurewhich is being reinforced in a high moisture environment, said structurebeing reinforced comprising: a structure comprising at least one surfacethat is located underwater; a reinforcement shell attached to at least aportion of said surface, said shell comprising a reinforcement layercomprising a fabric portion and a resin portion, said resin portioncomprising 80-120 parts by weight epoxy resin and 30-70 parts by weightof a conversion agent.
 11. A reinforced structure according to claim 10wherein said resin portion comprises 1 to 10 parts by weight of athickening agent.
 12. A reinforced structure according to claim 10 whichfurther comprises a containment layer located over said reinforcementshell.
 13. A reinforced structure according to claim 10 wherein saidfabric portion comprises fibers selected from the group consisting ofglass, polyaramid, graphite, silica, quartz, carbon, ceramic andpolyethylene.
 14. A reinforced structure according to claim 10 whereinsaid resin portion comprises an epoxy resin which is hydrogenated.
 15. Areinforced structure according to claim 10 wherein said portioncomprises a coloring agent.
 16. A reinforced structure according toclaim 10 wherein said conversion agent is a polyamino amid adduct,cycloaliphatic amine or modified amine.
 17. A structure according toclaim 10 wherein said resin portion has been cured to form a reinforcedstructure.
 18. A structure according to claim 11 wherein said resinportion has been cured to form a reinforced structure.
 19. A structureaccording to claim 14 wherein said resin portion has been cured to forma reinforced structure.
 20. A structure according to claim 15 whereinsaid resin portion has been cured to form a reinforced structure.